THE PLEISTOCENE OR GLACIAL PERIOD. 399 



The water-body at this stage is known as Lake Whittlesey (Fig. 

 518). 



At a still later stage, the Saginaw ice-lobe had retired into the 

 Huron basin, and the ponded waters in the Saginaw basin became 

 confluent with those in the Erie basin, which had, in the meantime, 

 become extended into the borders of the Ontario basin, but were blocked 

 in that direction by the Ontario ice-lobe. The extensive water body 

 thus developed is known as Lake Warren (Fig. 519). At first, this 

 lake discharged through the Grand River outlet into Lake Chicago ; but 

 later the eastern end appears to have worked its way along the south 

 border of the Ontario ice-lobe into the Finger Lake region of New 

 York, and to have reached at length the Mohawk valley, through 

 which it discharged into the Hudson, thus transferring the sea-con- 

 nection of the Erie basin from the Mexican Gulf to the Atlantic Ocean. 

 In the course of time, the shape of the water body centering about 

 the Ontario basin was changed as the ice retreated, and the Mohawk 

 outlet was lowered at the same time. Three successive stages of this 

 kind have been named Lake Dana, Lake Lundy, and Lake Iroquois 

 (Fig. 520), respectively, all discharging through the Mohawk. 



Meantime, the glacial lakes in the basins of Lake Michigan and 

 Superior experienced analogous shiftings of areas and of outlets. While 

 Lake Iroquois was discharging through the Mohawk valley, Lake 

 Algonquin (Fig. 521), formed by the coalescence of the glacial lakes 

 of the Superior, Michigan, and Huron basins, was discharging its waters 

 eastward. At first the outlet was probably by the St. Clair-Erie route, 

 through Lake Iroquois, to the Mohawk; but later, when the ice had 

 retired farther north, an outlet appears to have been effected from 

 Georgian bay, via the Trent river to Lake Iroquois (Fig. 521). This 

 lower outlet to the north was probably due to a depressed condition 

 of the area to the northeast, due to the weight of the ice mass and 

 the attraction of the latter on the water adjacent to it. 



When at length the Ontario ice withdrew from the Adirondacks 

 so far as to permit the ponded waters to find an outlet lower than that 

 by way of the Mohawk, between the ice and the north base of the 

 mountains, a new series of lowerings of the ponded water-body followed. 

 At first the outlet seems to have skirted the Adirondacks and emptied 

 into a glacially ponded water-body (glacial Lake Champlain) that occu- 

 pied the Champlain basin, and discharged southward into the Hudson. 



